2015-03-03T20:41:02ZInfluence of outlet flow temperature at EX07 heat exchangers of ALBA synchrotron cooling systemhttp://hdl.handle.net/2117/26564
Title: Influence of outlet flow temperature at EX07 heat exchangers of ALBA synchrotron cooling system
Authors: Escaler Puigoriol, Francesc Xavier
Abstract: The ALBA synchrotron cooling system relies in two heat exchangers (EX07 A and B) that transfer heat
from the system hot water to cold water coming from a cogeneration plant. As a result, the water
temperature can be reduced to a given set point. This temperature set point is currently fixed at 21° C.2015-03-03T13:58:16ZRecopilatori de les presentacions realitzades en el marc de la primera fase del modelat del sistema de refrigeració del sincrotró ALBAhttp://hdl.handle.net/2117/26563
Title: Recopilatori de les presentacions realitzades en el marc de la primera fase del modelat del sistema de refrigeració del sincrotró ALBA
Authors: Escaler Puigoriol, Francesc Xavier2015-03-03T13:31:44ZALBA cooling system 1D model and thermo-fluid dynamic simulations using Flowmaster® softwarehttp://hdl.handle.net/2117/26562
Title: ALBA cooling system 1D model and thermo-fluid dynamic simulations using Flowmaster® software
Authors: Escaler Puigoriol, Francesc Xavier
Abstract: The Center for Industrial Diagnostics and Fluid Dynamics (CDIF) is a R&D center within the Technical University of Catalonia (UPC). It belongs to the TECNIO network, a technology transfer initiative from ACC10, the Technology Innovation Agency of Catalonia. The CDIF provides technological support to industry in areas related to the field of fluid dynamics.
ALBA is a facility co-financed by the Spanish government and the Catalan government. ALBA is a new generation circular-shaped machine, called a synchrotron, which uses arrays of magnets, called insertion devices to generate bright beams of synchrotron light. Around the machine there are a collection of experimental research laboratories, called beamlines. At each beamline, scientists independently use the light generated by the machine for a wide variety of experiments.2015-03-03T13:23:21ZBoundary layer effects on the vortex shedding in a Donaldsontype hydrofoilhttp://hdl.handle.net/2117/24974
Title: Boundary layer effects on the vortex shedding in a Donaldsontype hydrofoil
Authors: Fontanals García, Alfred; Guardo Zabaleta, Alfredo de Jesús; Zobeiri, Amirreza; Egusquiza Estévez, Eduard; Farhat, Mohamed; Avellan, François
Abstract: Fluid - Structure Interaction (FSI) phenomena is becoming a relevant study field for the design or revamping of hydropower plants. The generalized trend of increasing flow rates and reducing rotor blades/stay vanes thickness in order to improve the efficiency of the machine together with a major push from plant owners/operators for production flexibility (partial load operation is more common nowadays) make the FSI between the vortex shedding
phenomenon and the vanes/blades of the machine an area of interest. From a design point of view, the machine structure has to resist all the hydrodynamic forces generated and maintain tension stresses under the fatigue limit to ensure a machine lifetime of several decades. To accomplish that goal, designers have to assure there is no presence of strong coupling
phenomena (lock-in) between the vortex shedding frequency and the eigenfrequencies of the structure.
As the vortex street is directly related to the state of the boundary layer along the hydrofoil, in this paper the effect of the boundary layer on the vortex shedding in a Donaldson-type hydrofoil is studied using Computational Fluid Dynamics (CFD). The development of the boundary layer along the Donaldson trailing edge hydrofoil chord is presented under lock-off conditions. The results are validated against previously obtained experimental results. Since the
Donaldson trailing edge is non-symmetric, the boundary layer velocity profiles are reported for the suction and pressure side of the hydrofoil. In addition, the effect of the Donaldson trailing edge on laminar-to-turbulent transition on both sides of the hydrofoil is studied.2014-12-10T10:33:08ZEstudio de sensibilidad de parámetros de modelos en flujos cavitantes en régimen no estacionariohttp://hdl.handle.net/2117/24972
Title: Estudio de sensibilidad de parámetros de modelos en flujos cavitantes en régimen no estacionario
Authors: Franco Cappa, E; Moll, Flavio; Coussirat Núñez, Miguel Gustavo; Gandolfo, Ernesto; Fontanals García, Alfred; Guardo Zabaleta, Alfredo de Jesús
Abstract: La cavitación es un complejo fenómeno físico que se presenta generalmente en flujos
turbulentos afectado por varios factores, como la presión del sistema y la concentración de gases no
condensables disueltos. Para analizar este comportamiento se han desarrollado modelos matemáticos,
algunos de los cuales se encuentran dentro de software de simulaciones comerciales.
Para ser aplicados, junto con modelos de turbulencia, deben fijarse cierto número de parámetros de
calibración que han sido establecidos sólo para un número reducido de tipos de flujo (geometrías
simples, variables del fluido típicas, flujo no desprendido, etc.). Cuando empieza a aparecer el flujo
reverso, incluso en geometrías simples, la capacidad de predecir correctamente el fenómeno de
cavitación es menor y se cree que un estudio cuidadoso de sensibilidad de parámetros es útil a la hora
de realizar aplicaciones de simulación a casos industriales.
Este trabajo amplía resultados ya obtenidos anteriormente, estudiando en detalle los modelos de mejor
comportamiento ya seleccionados, producto de la experiencia adquirida. Se busca ahora identificar la
mejor combinación de parámetros a través de la comparación de resultados experimentales de flujos
cavitantes, de características fuertemente no estacionarias, de típica aparición en turbomáquinas
hidráulicas (TMH), extendiendo los trabajos de calibración ya realizados anteriormente. Se ha seguido
utilizando geometrías simples (tipo Venturi) con el objeto de centrarse en los modelos de turbulencia y
cavitación ya probados para casos estacionarios y por tener una abundante información experimental de
flujos cavitantes en estas geometrías. Los trabajos de validación/calibración se llevaron a cabo
comparando perfiles de velocidad del fluido, la presión en la zona cavitante y la frecuencia del ciclo de
crecimiento y decrecimiento de la cavidad, entre otras variables, ajustando los coeficientes de
producción/disipación de energía turbulenta y algunos parámetros típicos del modelo de flujo cavitante
los que pueden influir en la exactitud y estabilidad de las predicciones numéricas.2014-12-10T09:49:31ZEstudio del fenómeno de interacción rotor estator (RSI) en una bomba radial, trabajando fuera de las condiciones de diseño óptimohttp://hdl.handle.net/2117/24944
Title: Estudio del fenómeno de interacción rotor estator (RSI) en una bomba radial, trabajando fuera de las condiciones de diseño óptimo
Authors: Coussirat Núñez, Miguel Gustavo; Fontanals García, Alfred; Panella, L; Guardo Zabaleta, Alfredo de Jesús
Abstract: El flujo en el interior de bombas radiales de altas prestaciones es difícil de describir, (geometría compleja y variable, flujo turbulento y no estacionario). La geometría compleja implica partes tanto móviles (rotor) como fijas (estator) con álabes, separadas por un huelgo pequeño que minimiza dimensiones de la máquina y que intenta optimizar la energía entregada al flujo. Al girar la máquina, su geometría varía, cambiando las condiciones del flujo en su interior. El flujo abandona el rotor entrando en el estator, llamado también difusor, generando el fenómeno de interacción rotor estator (RSI), de gran influencia en el comportamiento de la máquina, especialmente cuando ésta opera a caudales diferentes a los de condiciones de diseño óptimo. En este caso al operar fuera de condiciones de diseño, la complejidad del flujo se incrementa por aumentos de gradientes adversos de presión sobre la capa límite y/o desprendimientos de capa límite que influencian fuertemente el comportamiento general del flujo. Ya sea que se trabaje en condiciones de diseño o fuera de diseño, la RSI da lugar a pulsos de presión con frecuencias correlacionadas a las del giro de la máquina, las que también puede producir daños, ya que esas interacciones pueden tener un impacto significativo sobre las características vibratorias (e.g. acoplamiento con frecuencias propias) o acústicas de la máquina. En todos los casos el huelgo entre rotor y estator juega un papel fundamental en la intensidad de estos pulsos. Es sabido que bajo condiciones de diseño, el estudio de la RSI mediante el uso de simulaciones numéricas (CFD) del tipo estándar, esto es, uso de un esquema numérico basado en la técnica de Reynolds Averaged Navier Stokes equations (RANS) más un modelo de cierre para la turbulencia del tipo Eddy Viscosity Model (EVM) conduce a resultados bastante aceptables, sin comprometer seriamente recursos computacionales (memoria/tiempo de cálculo). Esto es debido a que la RSI es mucho más dependiente de los efectos de variación de la geometría (efecto potencial), que de la turbulencia del flujo, a diferencia de cuando la máquina trabaja fuera de las condiciones de diseño, donde el desprendimiento de capa límite afecta mucho la RSI, siendo en este caso la descripción del flujo más difícil mediante estos modelos. Para aplicaciones industriales de CFD a bombas que trabajan fuera del punto de diseño, situación cada vez más común, se requiere describir la RSI de una forma más completa. El objetivo de este trabajo es usar modelos de cierre más complejos, del tipo Scale-Adaptative Simulations (SAS), para ver las posibilidades de aplicación al diseño de bombas, ya que las opciones del tipo Large Eddy Simulations (LES) no pueden usarse aún debido a los altos requerimientos computacionales necesarios.2014-12-05T14:00:45ZVegetable oil tansesterification in supercritical conditions using Co-solvent carbon dioxide over solid catalysts: A screening studyhttp://hdl.handle.net/2117/24879
Title: Vegetable oil tansesterification in supercritical conditions using Co-solvent carbon dioxide over solid catalysts: A screening study
Authors: Saez, B; Santana, A; Ramírez-Llodra, E.; Maçaira Nogueira, Jose Miguel Lopes; Ledesma Rodriguez, Cristian; Llorca Piqué, Jordi; Larrayoz Iriarte, María Angeles
Abstract: The transesterification reaction employing supercritical methanol and carbon dioxide used as a co-solvent in the presence of several heterogeneous solid acid catalysts was investigated. The solid acid catalysts were prepared by impregnation methods, with appropriate precursors over magnesium aluminum silicate (cordierite). The catalysts tested were CeO2, WO3, ZnO, ZrO2, ZrO2-SO42-, mixed oxides (50-5096, w/w) WO3- ZrO2, CeO2-ZrO2, ZnO-La2O3, and Al2O3. Reaction tests were conducted at 200 degrees C and 20 MPa under the condition of 25:1 methanol/oil ratio at a space velocity of 4 mm with a fixed-bed continuous flow reactor containing ca. 5 g of catalyst. The best catalytic performance was obtained over ZrO2-SO42- with a yield toward fatty acid methyl esters (FAMEs) of 98%. This value is better to that obtained over the commercial catalyst Nafion SAC-13 (94%). The direct correlation between the conversion and catalyst total acidity was non-existent, but a positive effect of strong acid sites is evidenced.2014-11-28T10:30:37ZExperimental study on the added mass and damping of a disk submerged in a partially fluid-filled tank with small radial confinementhttp://hdl.handle.net/2117/24238
Title: Experimental study on the added mass and damping of a disk submerged in a partially fluid-filled tank with small radial confinement
Authors: Valentín Ruiz, David; Presas Batlló, Alexandre; Egusquiza Estévez, Eduard; Valero Ferrando, M.del Carmen
Abstract: The dynamic response of submerged and confined disk-like structures is of interest in engineering applications, such as in hydraulic turbine runners. This response is difficult to be estimated with accuracy due to the strong influence of the boundary conditions. Small radial gaps as well as short axial distances to rigid surfaces greatly modify the dynamic response because of the added mass and damping effects.
In this paper, the influence of the axial nearby rigid distance on the dynamic response of a submerged disk is evaluated when the radial gap is very small. Moreover, the effects of the fluid depth and fluid viscosity on the natural frequencies and damping ratio of the submerged disk are studied. The study has been performed experimentally and numerically using structural–acoustic simulations.
For the experimental investigation a test rig has been developed. It consists of a disk attached to a shaft and confined with a small radial gap inside a cylindrical container full of water. The disk can be moved up and down along the shaft to vary the axial distance to the nearby rigid surface. Piezoelectric patches are used to excite the disk and the response is measured with submersible accelerometers. Several excitation patterns can be used due to the disposition of these piezoelectric patches. For each configuration tested, the dynamic response of the structure is studied analyzing the natural frequencies and damping ratio of the disk attached to the shaft. The numerical results have been compared with the experimental results.2014-10-03T12:07:40ZProcess intensification using CO2 as cosolvent under supercritical conditions applied to the design of biodiesel productionhttp://hdl.handle.net/2117/22980
Title: Process intensification using CO2 as cosolvent under supercritical conditions applied to the design of biodiesel production
Authors: Maçaira, Jose; Santana, Aline; Oliveira Costa, Ana Carolina; Ramírez, E.; Larrayoz Iriarte, María Angeles
Abstract: In this work, a new process for biodiesel production under supercritical conditions in presence of cosolvent (CO2) is designed and simulated using the process simulator Aspen Plus. The model was developed using experimental reaction data of continuous catalytic biodiesel synthesis at a 74:25:1 CO2 to methanol to triglycerides molar ratio, temperature range between 150 and 300 C, at 250 bar. To decrease the temperature and pressure of operation and increase the conversion efficiency of biodiesel, CO2 was added as cosolvent to the reactants. Triolein (C 57H104O6) was chosen to represent the vegetal oil and methyl oleate (C19H36O2), biodiesel. A detailed kinetic model based on a three step reversible reaction scheme is used to describe the transesterification reaction in the process simulator. The simulated process resulted in full triolein conversion and a high purity (99.8%) fatty acid methyl esters product. The process plant was designed and simulated to operate in a continuous mode and the annual production capacity of the plant was set at 10000 tons. The total energy for the designed process was 2223 kW. On the basis of a preliminary economical study the minimum selling price of biodiesel is 0.83/L for a plant capacity of 10000 tons. A profitability analysis was conducted and the payback time was estimated as a function of the selling price and the plant capacity.2014-05-14T10:58:33ZEstudio mediante CFD de la interacción rotor-estator en una bomba centrífuga con difusorhttp://hdl.handle.net/2117/20664
Title: Estudio mediante CFD de la interacción rotor-estator en una bomba centrífuga con difusor
Authors: Coussirat Núñez, Miguel Gustavo; Fontanals García, Alfred; Guardo Zabaleta, Alfredo de Jesús
Abstract: Una bomba centrífuga con difusor, trabajando en diseño óptimo es estudiada por modelado numérico (CFD) con el fin de identificar y estudiar la posible amplificación de fluctuaciones de presión dentro de la máquina (RSI). Se usan resultados numéricos
previos, obtenidos en álabes aislados y cascadas de álabes fijos y móviles con
el objeto de validar/calibrar los modelos
para la turbulencia a utilizar, comparando
con los de bases de datos experimentales.
Este trabajo previo luego se aplica al estudio de la bomba con difusor, que servirá
para futuros estudios de turbomáquinas trabaj
ando bajo condiciones fuera de diseño en donde puede aparecer el fenómeno de
cavitación.2013-11-20T10:34:36ZAnalysis of the dynamic response of pump-turbine runners. Part I: Experimenthttp://hdl.handle.net/2117/18852
Title: Analysis of the dynamic response of pump-turbine runners. Part I: Experiment
Authors: Presas Batlló, Alexandre; Valero Ferrando, M.del Carmen; Huang, Xingxing; Egusquiza Estévez, Eduard; Farhat, Mohamed; Avellan, François
Abstract: When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed.2013-04-17T12:02:49ZPM21 Vibraciones Crepado Marzo 2011-Marzo 2013http://hdl.handle.net/2117/18787
Title: PM21 Vibraciones Crepado Marzo 2011-Marzo 2013
Authors: Escaler Puigoriol, Francesc Xavier2013-04-15T10:20:20ZExperimental investigation of added mass effects on a hydrofoil under cavitation conditionshttp://hdl.handle.net/2117/18433
Title: Experimental investigation of added mass effects on a hydrofoil under cavitation conditions
Authors: Torre Rodríguez, Óscar de la; Escaler Puigoriol, Francesc Xavier; Egusquiza Estévez, Eduard; Farhat, Mohamed
Abstract: The influence of leading edge sheet cavitation and supercavitation on the added mass effects experienced by a 2-D NACA0009 truncated hydrofoil has been experimentally investigated in a hydrodynamic tunnel. A non-intrusive excitation and measuring system based on piezoelectric patches mounted on the hydrofoil surface was used to determine the natural frequencies of the fluid–structure system. The appropriate hydrodynamic conditions were selected to generate a range of stable partial cavities of various sizes and also to minimize the effects of other sources of flow noise and vibrations. The main tests were performed for different sigma values under a constant flow velocity of 14 m/s and for incident angles of both 1° and 2°. Additionally, a series of experiments in which the hydrofoil was submerged in air, partially and completely submerged in still water and without cavitation at 7 and 14 m/s were also performed. The maximum added mass effect occurs with still water. When cavitation appears, the added mass decreases because the cavity length is increased, and the added mass is minimum for supercavitation. A linear correlation is found between the added mass coefficients and the entrained mass that accounts for the mean density of the cavity, its dimensions and its location relative to the specific mode shape deformation.2013-03-20T11:33:13ZNumerical and experimental analysis of the dynamic response of large submerged trash-rackshttp://hdl.handle.net/2117/17901
Title: Numerical and experimental analysis of the dynamic response of large submerged trash-racks
Authors: Huang, Xingxing; Valero Ferrando, M.del Carmen; Egusquiza Estévez, Eduard; Presas Batlló, Alexandre; Guardo Zabaleta, Alfredo de Jesús
Abstract: This paper investigates the effect of water in the dynamic response of large trash-racks used in hydropower plants. These are large structures that are fully submerged in water and located in the hydraulic circuits to prevent debris and large bodies from entering the turbine. These structures are prone to suffering fatigue damage. Broken bars are rather common, which can produce damage in the turbine and other hydraulic components.
To avoid fatigue problems, the trash-racks must be designed to avoid coincidence between the excitation frequencies of vortex shedding and the natural frequencies of the trash rack. Therefore, it is of paramount importance to know which are the natural frequencies and the associated mode-shapes, so as to avoid fluid–structure coupling (lock-in), which can lead to high vibration levels. Finite element models, including the surrounding mass of water, are used for this study.
The methodology is applied to two existing trash-racks by calculating the modal parameters and using the numerical finite element model. An experimental investigation is also carried out in one of the trash-racks by impacting the underwater grille and measuring the response using submergible accelerometers. Experimental modal analysis is utilized to extract the modal characteristics of the actual trash rack. There is a good agreement between the numerical and the experimental results. With the validated model, the effects of fluid added mass and damping on the dynamic response of both trash-racks are evaluated and discussed in order to extract some common conclusions.2013-02-21T08:58:02ZAnalysis if the dynamic response of pump-turbine runners- Part I: Experimenthttp://hdl.handle.net/2117/17894
Title: Analysis if the dynamic response of pump-turbine runners- Part I: Experiment
Authors: Presas Batlló, Alexandre; Valero Ferrando, M.del Carmen; Egusquiza Estévez, Eduard; Huang, Xingxing; Farhat, Mohamed; Avellan, François
Abstract: When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed.2013-02-20T11:36:21Z